A plant's status as annual or perennial often varies based on location. For example, a perennial plant in Georgia might easily be an annual plant in Michigan. This is because climatic conditions pay a large role in determining the length of a plant's life-cycle. If a normally biennial plant is grown in extremely harsh conditions it is likely to be treated as an annual because it will not survive the winter cold. Conversely, an annual grown under extremely favourable conditions may have such a highly successful propogation rate that it give the appearance of being bi- or perennial.
Annuals are often used in gardens to provide splashes of color, as they tend to produce more flowers than perennials. Also, many food plants are annuals, including most domesticated grains.
The life-cycle of an annual is very simple -- grow, flower, set seed and die. This can occur in a period as short as two or three months in some species. Many garden weeds are annuals.
See also biennial plant, perennial plant
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